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PHILADELPHIA 

Class  &<o<o- SBook  Un 3.3.  Accession 

REFERENCE 

Given  by  the  United  States  Government 


\ 


No.  28. 


PROFESSIONAL  PAPERS 

OF  THE 

CORPS  OF  ENGINEERS  OF  THE  UNITED  STATES  ARMY. 


PUBLISHED  BY  AUTHORITY  OF  THE  SECRETARY  OF  WAR. 


Headquarters,  Corps  of  Engineers. 

1901. 


PROFESSIONAL  PAPERS  OF  THE  CORPS  OF  ENGINEERS,  U.  S.  ARMY. 

No.  28. 


REPORT 


BOARD  OF  ENGINEER  OFFICERS 

ON 

TESTING  HYDRAULIC  CEMENTS, 

WITH 

SPECIFICATIONS  FOR  THE  SEVERAL  CLASSES 


USED  BY' 

THE  ENGINEER  DEPARTMENT. 


Major  WILLIAM  L.  MARSHALL, 

Major  SMITH  S.  LEACH, 

Captain  SPENCER  COSBY, 

Corps  of  Engineers,  U.  S.  Army,  Members  of  the  Board. 


WASHINGTON: 


GOVERNMENT  PRINTING  OFFICE. 


War  Department, 
Document  No.  144. 

Office  of  the  Chief  of  Engineers. 


Office  of  the  Chief  of  Engineers, 
United  States  Army, 

Washington , June  11 , 1901. 

Sir:  I have  the  honor  to  transmit  herewith  a report  of  a 
Board  of  Officers,  convened  under  your  authorit}7^  by  Special 
Orders,  No.  56,  Headquarters  Corps  of  Engineers,  1900,  to 
consider  and  report  upon  the  general  subject  of  manipulating 
and  testing  hydraulic  cements  used  in  the  public  works  car- 
ried on  under  the  supervision  of  this  office. 

The  Board  has  given  the  subject  careful  study,  and  its 
report,  which  is  accompanied  by  a proposed  draft  of  specifi- 
cations, is  recommended  for  approval  with  a view  of  securing 
uniform  practice  as  far  as  possible  throughout  the  Engineer 
Department. 

As  the  report  contains  much  information  that  is  valuable, 
not  only  to  the  Corps  of  Engineers,  but  also  to  the  engi- 
neering profession  at  large,  I further  recommend  that  1,000 
copies  be  printed  at  the  Government  Printing  Office  and  fur- 
nished for  the  use  of  this  office  on  the  customary  requisition. 

Very  respectfull}T,  your  obedient  servant, 

G.  L.  Gillespie, 

Brig.  Gen .,  Chief  of  Engineers, 

U.  S.  Army. 

Hon.  Elihu  Root, 

Secretary  of  War. 

[First  indorsement.]. 

Approved  as  within  recommended. 

By  order  of  the  Secretary  of  War: 

John  C.  Scofield, 

Chief  Clerk. 

War  Department,  June  19,  1901. 

5 


LETTER  OF  INSTRUCTIONS. 


Headquarters,  Corps  of  Engineers, 
United  States  Army, 

Washington , December  17 , 1900. 

Major:  In  view  of  the  lack  of  uniformity  that  exists  in  the 
specifications  for  cements  submitted  to  this  office  for  approval, 
it  is  considered  desirable  that  a uniform  set  of  specifications 
for  each  class  of  cement  should  be  prescribed  for  use  in  works 
under  the  supervision  of  this  office. 

The  Board  will  therefore  consider  the  general  subject  of 
testing  cements  and  make  such  recommendations  on  that  sub- 
ject as  will  be  applicable  under  the  conditions  prevailing  on 
the  works  carried  on  under  the  supervision  of  officers  of  the 
Corps  of  Engineers. 

The  Board  in  its  report  will  follow  in  a general  way  the 
report  of  the  Board  on  Electrical  Installations,  recently  sub- 
mitted, and,  after  its  remarks  and  recommendations,  will 
include  as  appendixes  to  the  report  sets  of  standard  specifica- 
tions for  both  Rosendale  and  American  Portland  cements 
which  shall  embrace  all  the  requirements  necessary  to  secure 
a suitable  cement. 

It  is  not  expected  that  the  Board  will  introduce  unnecessary 
refinements  in  the  tests  required,  but  will  bear  in  mind  the 
actual  conditions  that  obtain  in  the  Engineer  Department.  It 
is  desired,  however,  that  the  report  be  complete  and  authori- 
tative along  the  line  suggested. 

The  subject  of  slag  cements  has  recently  been  reported  on 
by  a Board  of  Engineer  Officers,  but  without  any  recommen- 
dations as  to  the  conditions  under  which  they  may  safely  be 
used.  The  Board  is  therefore  requested  to  consider  this  sub- 
ject, and  if  in  its  judgment  its  use  is  considered  admissible, 
it  is  requested  to  state  such  conditions  and  to  prepare  a set  of 
standard  specifications  for  slag  cements. 


8 


LETTER  OF  INSTRUCTIONS. 


In  view  of  the  possible  econom3r  resulting  to  the  Govern- 
ment from  its  grinding  together  cement  and  silica  sand,  it  is 
requested  that  this  subject  be  also  given  consideration  by  the 
Board. 

The  Board  is  authorized  to  call  upon  the  District  engineer 
officers  for  such  records  of  tests  or  such  other  information  as 
may  be  available. 

Very  respectfully, 

John  M.  Wilson, 

Brig.  Gen.,  Chief  of  Engineers, 

IT.  S.  Army. 

Maj.  W.  L.  Marshall, 

Corps  of  Engineers, 

President  of  Board  on  Specifications  for  Cements, 

New  York  City. 


REPORT. 


United  States  Engineer  Office, 

New  York  City , June  6y  1901. 

General:  The  Board  of  Officers  of  the  Corps  of  Engi- 
neers, constituted  by  Special  Orders,  No.  56,  Headquarters 
Corps  of  Engineers,  December  17, 1900,  has  the  honor  to  sub- 
mit the  following  report: 

The  Board  convened  at  the  Army  Building,  in  New  York 
City,  upon  the  call  of  the  senior  member,  at  10  a.  m.,  Jan- 
uary 8,  1901,  all  the  members  of  the  Board  being  present. 
At  sessions  held  on  that  and  the  following  da}T  the  Board 
arrived  at  a substantial  agreement  upon  the  leading  points  of 
the  subject  referred  to  it,  and  upon  the  general  wording  of 
the  specifications  for  the  several  classes  of  cement,  and  then 
adjourned  to  meet  at  the  call  of  the  senior  member  for  the 
completion  of  the  report. 

Under  the  authority  of  Special  Orders,  No.  3,  Headquarters 
Corps  of  Engineers,  January  12, 1901,  the  Board  reconvened  in 
New  York  City,  at  the  call  of  the  senior  member,  at  10  a.  m. , 
March  28,  1901.  During  a session  of  that  day  the  views  of  the 
several  members,  presented  in  writing,  were  carefully  consid- 
ered, and  the  Board  agreed  upon  a report  and  specifications. 
On  April  2 these  were  sent  to  the  Chief  of  Engineers,  but 
were  returned  to  the  Board  with  the  request  that  it  consider 
the  additional  subjects  of  sampling  the  cement,  amount  of 
testing  desirable  depending  on  the  importance  of  the  work 
and  the  size  of  the  order,  and  the  records  that  should  be  kept. 

At  the  call  of  the  senior  member,  and  b}T  authority  of  Spe- 
cial Orders,  No.  20,  Headquarters  Corps  of  Engineers,  May 
15,  1901,  the  Board  reassembled  in  New  York  City  at  10  a.  m., 
May  29,  and  formulated  its  report  upon  the  additional  sub- 
jects referred  to  it,  the  members  having  previously  communi- 

9 


10 


TESTING  HYDRAULIC  CEMENTS. 


cated  their  views  to  one  another  in  writing.  The  additional 
subjects  have  been  incorporated  in  the  following  report,  which 
is  accompanied  by  three  sets  of  proposed  specifications: 

GENERAL  CONSIDERATIONS. 

The  constructing  engineer  is  confronted  by  no  problem 
more  difficult  than  to  decide  whether  a certain  cement,  when 
placed  in  a work,  will  behave  in  a predetermined  way.  This 
is  especially  true  of  Portlands.  Other  cements  are  much 
more  reliable  under  conditions  of  exposure  for  which  they  are 
suited. 

The  difficulties  arise  from  the  fact  that  tests  for  acceptance 
or  rejection  must  be  made  on  a product  not  in  its  final  stage. 
A cement,  when  incorporated  in  masonry,  undergoes  for 
months  chemical  changes  in  the  process  of  setting,  so  that  the 
material  subjected  to  strains  in  the  work  is  not  the  material 
tested,  but  a derivative  of  it.  The  object  of  tests  is  to  estab- 
lish two  probabilities:  First,  that  the  product  of  the  given 
cement  will  develop  the  desired  strength  and  hardness  soon 
enough  to  enable  it  to  bear  the  stresses  designed  for  it;  sec- 
ond, that  it  will  never  thereafter  fall  below  that  strength 
and  hardness.  Up  to  the  present  time  it  appears  that  the 
relation  between  the  chemical  and  physical  properties  of  raw 
cement  and  of  its  partially  indurated  derivatives,  determined 
by  tests,  and  the  physical  properties  of  the  same  cement  or 
its  derivatives,  after  complete  hydration  and  induration  in  the 
work,  can  be  stated  only  within  rather  wide  limits. 

The  most  useful  tests  of  cements  are  those,  first,  which  con- 
nect themselves  definitely  with  some  serious  defect  to  which 
cements  &re  subject,  or  with  some  merit  which  they  should 
possess;  second,  which  can  be  made  with  the  least  apparatus 
and  manipulation,  and  which  give  their  indications  in  the 
shortest  time;  and,  third,  which  are  freest  from  personal 
equation  and  from  influences  of  local  surroundings.  These 
criteria,  applied  to  the  customary  tests  of  cements,  give  indi- 
cations as  to  their  relative  value  and  the  best  methods  of 
making  them. 

TEST  OF  GRINDING. 

This  test  derives  importance  from  the  fact,  apparently  well 
established,  that,  other  things  being  equal,  the  finer  the 


TESTING  HYDRAULIC  CEMENTS. 


11 


cement  the  greater  will  be  its  sand-carrying  capacity;  that  is, 
it  will  show  greater  strength  with  the  same  charge  of  sand, 
or  equal  strength  with  a greater  charge.  According  to  the 
best  information  the  Board  can  obtain,  the  cementitious  value 
of  this  material  is  believed  to  reside  principally,  if  not 
wholly,  in  the  very  fine  part.  It  follows  that  a grinding  test 
should  be  directed  to  determining  the  proportion  which  is 
very  fine  rather  than  the  residue  above  a certain  size.  The 
Board  does  not  propose  any  change  in  the  accepted  grinding 
test  of  Portland  cement,  but  favors  for  Natural  cement  the 
use  of  the  same  size  screen  as  for  Portland,  No.  100,  with  the 
requirement  that  80  per  cent  shall  pass  through  it.  The 
screen  should  be  frequently  examined,  magnified,  if  practi- 
cable, to  see  that  no  wires  are  displaced  leaving  apertures 
larger  than  the  normal. 

TEST  FOR  SPECIFIC  GRAVITY. 

This  test  is  made  with  simple  appliances,  and  its  result  is 
immediately  known.  It  appears  to  connect  itself  quite  defi- 
nitely with  the  degree  of  calcination  which  the  cement  has 
received.  The  higher  the  burning,  short  of  vitrification,  the 
better  the  cement  and  the  higher  the  specific  gravity. 

This  test  has  another  value,  in  that  the  adulterations  of 
Portland  cement  most  likely  to  be  practiced  and  most  to  be 
feared  are  made  with  materials  which  reduce  the  specific 
gravity.  The  test  is  therefore  of  value  in  determining  a 
properly  burned,  nonadulterated  Portland.  If  underburned, 
the  specific  gravity  may  fall  below  3;  it  may  reach  3.5  if  the 
cement  has  been  overburned.  No  other  hydraulic  cement  is 
so  heavy  in  proportion  to  volume,  Natural  cement  having  a 
specific  gravity  of  about  2.5  to  2.8  and  Puzzolan  (slag)  of 
about  2.7  to  2.8.  Properly  burned  Portland,  adulterated  with 
slag,  will  fall  below  3.1. 

TEST  OF  ACTIVITY. 

This  test,  made  by  gauging  the  cement  with  water  and 
observing  the  times  of  initial  and  permanent  set,  is  partly 
direct  and  partly  indirect.  It  is  direct  in  so  far  as  its  limits 
relate  to  the  time  necessary  to  get  the  cement  in  place  after 
mixing,  which  must  not  be  greater  than  the  time  of  initial 
set,  and  to  the  time  within  which  the  cement  product  must 


12 


TESTING  HYDRAULIC  CEMENTS. 


take  its  load,  which  must  not  be  less  ,than  the  time  of  perma- 
nent set.  It  is  indirect  in  so  far  as  its  limits  relate  to  the 
probable  final  strength,  elasticity,  and  hardness  of  the  cement 
mixtures.  In  the  latter  respect  it  appears  to  be  reasonably 
well  established  that  cements  exhibiting  great  activity  give, 
after  long  periods,  results  inferior  to  those  with  action  less 
rapid. 

The  test  for  activity  is  easily  made  with  simple  appliances, 
and  its  results  are  known  in  a few  hours  at  most.  Variable 
results  in  the  test  are  caused  by  different  local  conditions  of 
moisture  and  temperature  and  by  the  different  judgments 
of  observers  as  to  whether  the  needles  penetrate  or  not.  Gen- 
erally speaking,  both  periods  of  set  are  lengthened  by  increase 
of  moisture  and  shortened  b}T  increase  of  temperature.  Some 
manufacturers  claim  that  their  cements  show  their  best  results 
when  gauged  with  particular  percentages  of  water.  It  is  not 
considered  good  policy  to  encourage  these  peculiarities  at  the 
expense  of  the  uniformity  of  tests  which  is  so  greatl}T  desired. 
It  is  better  to  adopt  a definite  proportion  of  water  for  gauging 
and  require  all  cements  of  the  same  class  to  stand  or  fall  on 
their  showing  when  so  gauged.  Such  a percentage,  adopted 
and  known,  will  probably  be  used  by  manufacturers  in  testing 
goods  sold  to  the  Engineer  Department,  and  a greater  har- 
mony between  mill  and  field  tests  of  the  same  cement  will 
result. 

In  gauging  Portland  cement  in  damp  weather  the  samples 
should  be  thoroughhT  dried  before  adding  water.  This  pre- 
caution is  not  deemed  necessaiy  with  Natural  cement.  Suf- 
ficient uniformity  of  temperature  will  result  if  the  testing 
room  be  comfortably  warmed  in  winter  and  the  specimens  be 
kept  out  of  the  sun  in  a cool  room  in  summer,  and  under  a 
damp  cloth  until  set. 

TEST  FOR  CONSTANCY  OF  VOLUME. 

This  test  results  from  observations  made  on  the  pats  or 
cakes  used  in  the  setting  test.  It  derives  its  value  from  its 
connection  with  the  quantit}r  of  expansives  in  the  cement. 

The  test  is  easy  to  make,  and  its  results  are  relative^  free 
from  personal  error,  though  there  is  room  for  a difference  of 
judgment  as  to  the  appearance  of  the  cakes.  As  they  may 
be  preserved  and  the  decision  reviewed  at  any  time  on  the 
original  data,  such  differences  are  immaterial. 


TESTING  HYDRAULIC  CEMENTS. 


13 


TESTS  OF  STRENGTH. 

These  may  be  subdivided  into  compressive  and  tensile  tests, 
the  latter  including  the  transverse  test  made  by  breaking  a 
beam  of  the  cement.  The  compressive  test  need  not  be  fur- 
ther considered,  as  it  is  less  easily  made  than  the  tensile  test 
and  gives  no  surer  indications.  The  ratio  of  compressive  to 
tensile  strength  of  the  same  class  of  cements  is  quite  uniform. 

Of  the  tensile  tests  the  direct  pull  is  preferable  to  the 
flexure  test. 

The  tensile  test  is  theoretically  a perfect  index  of  the  quality 
of  the  cement  at  the  periods  of  test,  and  a comparison  at  dif- 
ferent periods  gives  the  best  obtainable  indication  of  what  its 
subsequent  conduct  will  be.  In  the  opinion  of  the  Board  the 
two  periods  most  generally  adopted,  seven  and  twenty-eight 
days  after  mixing,  are,  on  the  whole,  the  best.  The  one-day 
test,  though  of  some  value  in  a discriminating  sense,  should 
not  be  placed  in  the  same  category  as  the  other  periods  named. 

The  apparatus  for  tensile  tests  is  somewhat  elaborate  and 
delicate,  but  is  of  standard  manufacture  and  readily  obtainable 
at  relatively  small  cost. 

In  respect  of  uncertainties  due  to  the  personal  equation  of 
the  tester  and  to  the  influence  of  local  conditions  this  test  pre- 
sents greater  difficulties  than  any  of  the  others  considered. 
The  most  scrupulous  care  must  be  observed  in  the  manipula- 
tions, and  the  tester  should  possess  natural  aptitude  for  such 
work.  The  object  is  to  determine  the  greatest  stress  per 
square  inch  which  the  cement  can  be  made  to  stand  under 
given  conditions  without  rupture.  If  the  conditions  have 
been  carefully  observed  and  several  discrepant  results  are 
obtained,  the  highest  may  be  right,  but  the  others  are  cer- 
tainly wrong.  No  averaging  should  be  done. 

The  remarks  made  above  under  the  activity  test  as  to  the 
relation  between  early  hydraulic  intensity  and  the  final  excel- 
lence of  a cement  product  are  equally  applicable  to  the  indica- 
tions from  tensile  tests.  A cement  which  tests  moderately 
high  at  seven  days  and  shows  a substantial  increase  to  twenty- 
eight  days  is  more  likely  to  reach  the  maximum  strength 
slowly  and  retain  it  indefinitely  with  a low  modulus  of  elas- 
ticity than  a cement  which  tests  abnormally  high  at  seven 
days  with  little  or  no  increase  at  twenty-eight  days. 


14 


TESTING  HYDRAULIC  CEMENTS. 


ACCELERATED  TESTS. 

The  rules  recommended  by  the  committee  of  the  American 
Society  of  Civil  Engineers  in  1885  have  been  substantially 
accepted  here  and  abroad  as  to  tests  of  setting  qualities  and 
soundness;  more  rapid  tests  for  soundness  are,  however,  pro- 
posed and  practiced,  though  no  accelerated  test  has  been  gen- 
erally accepted. 

Accelerated  tests  proposed  for  the  speedy  detection  of  the 
presence  of  expansives  in  cement  usually  consist  in  the  appli- 
cation, after  gauging,  of  dry  heat  or  of  immersion  in  warm  or 
boiling  water  or  steam.  The  immersion  tests  are  most  in 
vogue.  Thej'  vary  from  immersing  freshly  gauged  pats  on 
glass  plates  in  water  at  115°  F.  for  twenty-four  hours,  or  at 
higher  temperatures  for  various  periods,  to  steaming  or  boil- 
ing cakes  or  cylinders  of  the  material  to  be  tested  at  212°  F. 
for  varying  times. 

In  France  and  Germany  the  swelling  or  expansion  of  boiled 
cylinders  is  measured  directly  by  calibration.  Usually  change 
of  volume  not  accompanied  by  visible  evidences  of  it — i.  e. , dis- 
tortion or  disruption — is  not  observed  in  American  tests  pre- 
scribed in  specifications  for  the  reception  of  cements.  Of  all 
these  tests  the  boiling  test  is  the  simplest  , requires  onl}r  appa- 
ratus everywhere  available,  and  is  recommended  b}r  the  Board. 
It  has  been  the  experience  that  this  test  detects  material  that 
is  unsound  by  reason  of  the  presence  of  active  expansives; 
but  in  some  cases  it  rejects  material  that  would  give  satisfac- 
tory results  in  actual  work  and  will  reject  material  that  would 
stand  this  test  after  air  slaking. 

The  great  value  of  the  test  lies  in  its  short-time  indications 
and  in  at  once  directing  attention  to  weak  points  in  the  cement 
to  be  further  observed  or  guarded  against.  Of  two  or  more 
cements  offered  for  use  or  on  hand,  the  cements  that  stand  the 
boiling  tests  are  to  be  taken  preferably;  it  should  be  con- 
stantly applied  on  the  work  among  other  simple  tests  to  be 
noted,  for  although  the  boiling  test  sometimes  rejects  suitable 
material,  it  is  believed  that  it  will  always  reject  a material  un- 
sound by  reason  of  the  existence  of  active  expansives.  Sul- 
phate of  lime,  while  enabling  cements  to  pass  the  boiling  tests, 
introduces  an  element  of  danger. 


TESTING  HYDRAULIC  CEMENTS. 


15 


This  test  is  proposed  as  suggestive  or  discriminative  only. 
Except  for  works  of  unusual  importance  it  is  not  recommended 
that  a cement  passing  the  other  tests  proposed  shall  be  rejected 
on  the  boiling  test. 


TESTS  TO  BE  MADE. 

For  selecting  Portland  and  Puzzolan  cement  from  among 
the  brands  offered,  the  Board  recommends  that  the  following 
tests  be  made: 

1.  For  fineness  of  grinding. 

2.  For  specific  gravity. 

3.  For  soundness,  or  constancy  of  volume  in  setting. 

1.  For  time  of  setting. 

5.  For  tensile  strength. 

For  Natural  cement  we  recommend  the  omission  of  the 
specific-gravity  and  soundness  tests. 

On  the  works  the  Board  recommends  simple  tests  when  the 
more  elaborate  tests  can  not  well  be  made. 

In  determining  the  minimum  requirements  for  cements 
given  in  the  subjoined  specifications  we  recognize  that  many 
cements  that  attain  only  fair  strength  neat  and  with  sand  in  a 
short  time  and  show  marked  gains  of  strength  on  further 
time  will  fulfill  the  requirements  of  the  service,  and  that  unusu- 
ally high  tensile  strength  attained  in  a few  days  after  gaug- 
ing is  often  coupled  with  a small  or  negative  increase  in 
strength  in  further  short  intervals.  Unusually  high  tests  in 
a short  time  after  gauging  should  be  regarded  with  suspicion, 
although  some  well-known  brands  of  American  cements  show 
great  strength  in  short-time  tests  and,  so  far  as  observed,  are 
reliable  in  air  and  fresh  water.  Cements  offered  under  such 
known  brands  should  show  their  characteristic  strength  and 
other  qualities  or  be  suspected  as  spurious  or  adulterated,  if 
not  rejected,  even  though  the  minimum  requirements  of  the 
specifications  are  met.  The  practice  of  offering  a bonus  or 
free  gift  of  money  in  addition  to  the  contract  price  for  cement 
testing  above  a fixed  high  point  should  be  prohibited  as  un- 
necessary, for  cements  so  obtained  are  likely  to  be  unsound 
in  a manner  not  easily  detected  in  the  time  usually  available 
in  testing. 


16 


TESTING  HYDRAULIC  CEMENTS. 


It  is  believed  that  most  of  the  very  high  testing  Portland 
cements  have  lime  in  excess,  the  effect  of  which  is  tempo- 
rarily masked  by  the  use  of  sulphate  of  lime.  Overlimed 
cements  so  treated  are  unfit  for  use  in  sea  water.  For  such 
uses  a chemical  analysis  should  be  required,  and  the  quantity 
of  sulphuric  acid,  as  well  as  magnesia,  be  limited  to  a low  per- 
centage. It  is  not  yet  known  that  sulphate  of  lime  in  quan- 
tity less  than  2 per  cent  is  injurious  to  cements  to  be  used  in 
fresh  water  or  in  air.  It  masks  expansives  .that  might  ulti- 
mately cause  the  destruction  of  the  work,  but  it  is  not  known 
whether  this  effect  is  permanent.  Its  addition  is  now  deemed 
necessary  to  control  time  of  setting.  It  makes  a quick-setting 
cement  slow  setting,  at  the  same  time  increasing  tensile 
strength  acquired  in  short  time. 

MANIPULATION  OF  CEMENTS  FOR  TESTS. 

I.  Fineness. 

Place  100  parts  (denominations  determined  by  subdivisions 
of  the  weighing  machine  used)  by  weight  on  a sieve  with  100 
holes  to  the  linear  inch,  woven  from  brass  wire  No.  40,  Stubb’s 
wire  gauge;  sift  by  hand  or  mechanical  shaker  until  cement 
ceases  to  pass  through. 

The  weight  of  the  material  passing  the  sieve  plus  the  weight 
of  the  dust  lost  in  air,  expressed  in  hundredths  of  the  original 
weight,  will  express  the  percentage  of  fineness.  In  order  to 
determine  this  percentage  the  residue  on  the  sieve  should  be 
weighed. 

It  is  only  the  impalpable  dust  that  possesses  cementitious 
value.  Fineness  of  grinding  is  therefore  an  essential  quality 
in  cements  to  be  mixed  with  sand.  The  residue  on  a sieve  of 
100  meshes  to  the  inch  is  of  no  cementitious  value,  and  even 
the  grit  retained  on  a sieve  of  40,000  openings  to  the  square 
inch  is  of  small  value.  The  degree  of  fineness  prescribed  in 
these  specifications  (92  per  cent)  for  Portland  through  a sieve 
of  10,000  meshes  to  the  square  inch  is  quite  commonly  attained 
in  high-grade  American  cements,  but  rarely  in  imported 
brands.  On  the  Pacific  coast,  where  foreign  cements  only 
are  in  the  market,  this  requirement  may  be  lowered  for  the 
present  to  87  per  cent  on  No.  100  sieve. 


TESTING  HYDRAULIC  CEMENTS. 


IT 


. II.  Specific  gravity. 

The  standard  temperature  for  specific  gravity  determina- 
tions is  62°  F.,  but  for  cement  testing  temperatures  may 
vary  between  60°  and  80°  F.  without  affecting  results  more 
than  the  probable  error  in  the  observation. 

Use  any  approved  form  of  volumenometer  or  specific  grav- 
ity bottle,  graduated  to  cubic  centimeters  with  decimal  sub- 
divisions. Fill  instrument  to  zero  of  the  scale  with  benzine, 
turpentine,  or  some  other  liquid  having  no  action  upon  cements. 

Take  100  grams  of  sifted  cement  that  has  been  previously 
dried  by  exposure  on  a metal  plate  for  twenty  minutes  to  a 
diy  heat  of  212°  F. , and  allow  it  to  pass  slowly  into  the  fluid 
of  the  volumenometer,  taking  care  that  the  powder  does  not 
stick  to  the  sides  of  the  graduated  tube  above  the  fluid  and 
that  the  funnel  through  which  it  is  introduced  does  not  touch 
the  fluid. 

Read  carefully  the  volume  of  the  displaced  fluid  to  the  near- 
est fraction  of  a cubic  centimeter.  Then  the  approximate 
specific  gravity  will  be  represented  by  100  divided  by  the 
displacement  in  cubic  centimeters. 

The  operation  requires  care. 

III.  Setting  qualities  and  soundness. 

The  quantity  of  water  and  the  temperature  of  water  and 
air  affect  the  time  of  setting.  The  specifications  contemplate 
a temperature  varying  not  more  than  10°  from  62°  F.,  and 
quantities  of  water  given  herein : 

For  Portland  cements  use  20  per  cent  of  water. 

For  Puzzolan  cements  use  18  per  cent  of  water. 

For  Natural  cements  use  30  per  cent  of  water. 

Mix  thoroughly  for  five  minutes,  vigorously  rubbing  the 
mixture  under  pressure;  time  to  be  estimated  from  moment 
of  adding  water  and  to  be  considered  of  importance. 

Make  on  glass  plates  two  cakes  from  the  mixture  about 
three  inches  in  diameter,  half  an  inch  thick  at  middle,  and 
drawn  to  thin  edges,  and  cover  them  with  a damp  cloth  or 
place  them  in  a tight  box  not  exposed  to  currents  of  dry  air. 
At  the  end  of  the  time  specified  for  initial  set  apply  the  needle 

1593—01 2 


18 


TESTING  HYDKAULIC  CEMENTS. 


one-twelfth  of  an  inch  diameter  weighted  to  one-fourth  of  a 
pound  to  one  of  the  cakes.  If.  an  indentation  is  made  the 
cement  passes  the  requirement  for  initial  setting,  if  no  inden- 
tation is  made  by  the  needle  it  is  too  quick  setting.  At  the 
end  of  the  time  specified  for  “ final  set”  apply  the  needle  one 
twenty-fourth  of  an  inch  diameter  loaded  to  one  pound.  The 
cement  cake  should  not  be  indented. 

Expose  the  two  cakes  to  air  under  damp  cloth  for  twenty  - 
four  hours.  Place  one  of  the  cakes,  still  attached  to  its  plate, 
in  water  for  twenty-eight  days;  the  other  cake  immerse  in 
water  at  about  70°  temperature  supported  in  a rack  above  the 
bottom  of  the  receptacle;  raise  the  water  gradually  to  the 
boiling  point  and  maintain  this  temperature  for  six  hours  and 
then  let  the  water  with  cake  immersed  cool.  Examine  the 
cakes  at  the  proper  time  for  evidences  of  expansion  and  dis- 
tortion. Should  the  boiled  cake  become  detached  from  the 
plate  hy  twisting  and  warping  or  show  expansion  cracks  the 
cement  may  be  rejected,  or  it  may  await  the  result  of  twenty- 
eight  days  in  water.  If  the  fresh-water  cake  shows  no  evi- 
dences of  swelling,  the  cement  may  be  used  in  ordinary  work 
in  air  or  fresh  water  for  lean  mixtures.  If  distortion  or 
expansion  cracks  are  shown  on  the  fresh -water  cake,  the 
cement  should  be  rejected. 

Of  two  or  more  cements  offered,  all  of  which  will  stand  the 
fresh-water  cake  test  for  soundness,  the  cements  that  will 
stand  the  boiling  tests  also  are  to  be  preferred. 

IV.  Tensile  strength. 

Neat  test's. — -Use  unsifted  cements.  Place  the  amount  to  be 
mixed  on  a smooth,  nonabsorbent  slab;  make  a crater  in  the 
middle  sufficient  to  hold  the  water;  add  nearly  all  the  water 
at  once,  the  remainder  as  needed;  mix  thoroughly  by  turning 
with  the  trowel,  and  vigorously  rub  or  work  the  cement  for 
five  minutes. 

Place  the  mold  on  a glass  or  slate  slab.  Fill  the  mold  with 
consecutive  layers  of  cement,  each  when  rammed  to  be  one- 
fourth  of  an  inch  thick.  Tap  each  layer  30  taps  with  a soft 
brass  or  copper  rammer  weighing  1 pound  and  having  a face 
three-fourths  of  an  inch  diameter  or  seven-tenths  of  an  inch 
square  with  rounded  corners.  The  tapping  or  ramming  is  to 


TESTING  HYDRAULIC  CEMENTS. 


19 


be  done  as  follows:  while  holding  the  forearm  and  wrist  at  a 
constant  level,  raise  the  rammer  with  the  thumb  and  fore- 
finger about  half  an  inch  and  then  let  it  fall  freely,  repeating 
the  operation  until  the  layer  is  uniformly  compacted  by  30 
taps. 

This  method  is  intended  to  compact  the  material  in  a man- 
ner similar  to  actual  practice  in  construction,  when  a metal 
rammer  is  used  weighing  30  pounds,  with  circular  head  5 
inches  in  diameter  falling  about  8 inches  upon  layers  of  mortar 
or  concrete  3 inches  thick.  The  method  permits  comparable 
results  to  be  obtained  by  different  observers. 

After  filling  the  mold  and  ramming  the  last  layer,  strike 
smooth  with  the  trowel,  tap  the  mold  lightly  in  a direction 
parallel  to  the  base  plate  to  prevent  adhesion  to  the  plate,  and 
cover  for  twenty-four  hours  with  a damp  cloth.  Then  remove 
the  briquette  from  the  mold  and  immerse  it  in  fresh  water, 
which  should  be  renewed  twice  a week  for  the  specified  time 
if  running  water  is  not  available  for  a slow  current.  If  molds 
are  not  available  fortwenty-four  hours,  remove  from  the  molds 
after  final  set,  replacing  the  damp  cloth  over  the  briquettes. 
In  removing  briquettes  before  hard-set  great  care  should  be 
exercised.  Hold  the  mold  in  the  left  hand  and,  after  loosening 
the  latch,  tap  gently  the  sides  of  the  mold  until  they  fall  apart. 
Place  the  briquettes  face  down  in  the  water  trough. 

For  neat  tests  of  Portland  cement  use  20  per  cent  of  water 
by  weight. 

For  neat  tests  of  Puzzolan  cement  use  18  per  cent  of  water 
by  weight. 

For  neat  tests  of  Natural  cement  use  30  per  cent  of  water 
by  weight. 

Nearly  all  this  water  is  retained  by  Portland  cement,  whereas 
only  about  one-third  of  the  gauging  water  is  retained  by  Puz- 
zolan or  Natural  cements;  from  this  it  follows  that  an  apparent 
condition  of  plasticity  or  fluidity  that  ultimately  little  injures 
Portland  paste,  very  seriously  injures  Puzzolan  or  Natural 
mortars  and  concretes  by  leaving  a porous  texture  on  the 
evaporation  of  the  surplus  wTater. 

Sand  tests. — The  proportions  1 cement  to  3 sand  are  to  be 
used  in  tests  of  Puzzolan  and  Portland,  and  1 cement  to  1 sand 
in  tests  of  Natural  or  Rosendale  cements.  Crushed  quartz 


20 


TESTING  HYDRAULIC  CEMENTS. 


sand,  sifted  to  pass  a standard  sieve  with  20  meshes  per  linear 
inch  and  to  be  retained  on  a standard  sieve  with  30  meshes  to 
the  inch,  is  to  be  used. 

After  weighing  carefully,  mix  dry  the  cement  and  sand 
until  the  mixture  is  uniform,  add  the  water  as  in  neat  mix- 
tures, and  mix  for  five  minutes  by  triturating  or  rubbing 
together  the  constituents  of  the  mortar.  This  may  be  done 
under  pressure  with  a trowel  or  by  rubbing  between  the  fin- 
gers, using  rubber  gloves.  The  rubbing  together  seems  nec- 
essary to  coat  thoroughly  the  facets  of  the  sand  with  the 
cement  paste. 

It  is  found  that  prolonged  rubbing,  when  not  carried  beyond 
the  time  of  initial  set,  results  in  higher  tests.  Five  minutes 
is  the  time  of  mixing  quite  generally  adopted  in  European 
specifications.  The  briquettes  are  to  be  made  as  prescribed 
for  neat  mixtures. 

Portland  cements  require  water  from  11  to  12^  per  cent  by 
weight  of  constituent  sand  and  cement  for  maximum  strength 
in  tested  briquettes. 

Puzzolan,  about  9 to  10  per  cent. 

Natural,  about  15  to  17  per  cent. 

Mixtures  that  at  first  appear  too  dry  for  testing  purposes 
often  become  more  plastic  under  the  prolonged  working 
required  herein. 

In  general,  about  four  briquettes  constitute  the  maximum 
number  that  may  be  made  well  within  the  time  required  for 
initial  setting  of  moderately  slow  setting  cements. 

Three  such  batches  of  sand  mixtures  should  be  made,  and 
one  briquette  of  each  batch  may  be  broken  at  seven  and 
twenty-eight  days,  giving  three  tests  at  each  period.  At 
least  one  batch  of  neat  cement  briquettes  should  be  made. 

If  the  first  briquette  broken  at  each  date  fulfills  the  mini- 
mum requirement  of  these  specifications  it  is  not  necessary  to 
break  others  which  may  be  reserved  for  long-time  tests. 

If  the  first  briquette  does  not  pass  the  test  for  tensile 
strength,  then  briquettes  may  be  broken  until  six  briquettes* 
two  from  each  batch,  have  been  broken  at  seven  days,  and  the 
remaining  six  reserved  for  twenty-eight-day  tests.  The  high- 
est result  from  any  sample  is  to  be  taken  as  the  strength  of 
the  sample  when  the  break  is  at  the  least  section  of  briquette. 

If,  on  the  twenty-eight-day  tests,  the  cement  not  only  more 


TESTING  HYDRAULIC  CEMENTS. 


21 


than  fulfills  the  minimum  requirements  of  these  specifications, 
but  also  shows  unusual  gain  in  strength,  it  may  still  be  accepted 
if  the  other  tests  are  satisfactory,  notwithstanding  a low  seven- 
day  test,  if  early  strength  is  not  a matter  of  importance.  Such 
cements  are  likety  to  be  permanent. 

For  a batch  of  four  briquettes,  the  following  quantities  are 
suggested  as  in  accord  with  these  specifications.  Water  is 
measured  b}T  fluid-ounce  volumes,  not  by  weight,  temperature 
varying  not  more  than  10°  from  62°  F. 

PORTLAND  CEMENT. 

Neat:  20  ounces  of  cement,  1 ounces  of  water.  Mix  wet 
five  minutes. 

Sand:  15  ounces  sand,  5 ounces  cement,  2-J-  ounces  water. 
Mix  thoroughly  dry;  then  mix  wet  five  minutes. 

PUZZOLAN  CEMENT. 

Neat:  20  ounces  cement,  3f  ounces  water.  Mix  wet  five 
minutes. 

Sand:  15  ounces  sand,  5 ounces  cement,  2 ounces  water. 
Mix  thoroughly  dry;  then  mix  wet  five  minutes. 

NATURAL  CEMENT. 

Neat:  20  ounces  cement,  6 ounces  water.  Mix  wet  five 
minutes. 

Sand:  10  ounces  cement,  10  ounces  sand,  3£  ounces  water. 
Mix  dry;  then  wet  for  five  minutes. 

For  measuring  tensile  strength,  a machine  that  applies  the 
stress  automatically  at  a uniform  rate  is  preferable  to  one 
controlled  entirely  by  hand. 

These  specifications  for  tensile  strength  contemplate  the 
application  of  stress  at  the  rate  of  400  pounds  per  minute  to 
briquettes  made  as  prescribed  herein.  A rate  so  rapid  as  to 
approximate  a blow  or  so  slow  as  to  approximate  a continued 
stress  will  give  very  different  results. 

The  tests  for  tensile  strength  are  to  be  made  immediately 
after  taking  from  the  water  or  while  the  briquettes  are  still 
wet.  The  temperature  of  the  water  during  immersion  should 
be  maintained  as  nearly  constant  as  practicable;  not  less  than 
50°  nor  more  than  70°  F. 


22 


TESTING  HYDRAULIC  CEMENTS. 


The  tests  are  to  be  made  upon  briquettes  1 inch  square  at 
place  of  rupture.  The  specifications  contemplate  the  use  of 
the  form  of  briquette  recommended  by  the  committee  of  the 
American  Society  of  Civil  Engineers,  held  when  tested  by 
close-fitting  metal  clips,  without  rubber  or  other  jdelding 
contacts.  The  breaks  considered  in  the  tests  are  to  be  those 
occurring  at  the  smallest  section,  1 inch  square. 

SIMPLE  TESTS. 

Tests  of  cement  received  upon  a work  in  progress  must 
often  be  of  much  simpler  character  than  prescribed  herein. 

Tests  on  the  work  are  mainly  to  ascertain  whether  the 
article  supplied  is  genuine  cement,  of  a brand  previously 
tested  and  accepted,  and  whether  it  is  a reasonably  sound  and 
active  cement  that  will  set  hard  in  the  desired  time,  and  give 
a good,  hard  mortar.  Simple  tests  may  give  this  information, 
and  such  should  be  multiplied  whether  or  not  more  elaborate 
tests  be  made.  Pats  and  balls  of  cement  and  mortar  from 
the  storehouse  and  mixing  platform  or  machine  should  be 
frequently  made.  The  setting  or  hardening  qualities,  as  de- 
termined roughly  by  estimating  time  and  by  pressure  of  the 
thumbnail,  should  be  observed;  the  hardness  of  the  set  and 
strength,  by  cracking  the  hardened  pats  or  cakes  between  the 
fingers,  and  by  dropping  the  balls  from  the  height  of  the  arm 
upon  a pavement  or  stone  and  observing  the  result  of  the 
impact. 

By  placing  the  pats  in  water  as  soon  as  hardened  sufficiently 
and  raising  the  temperature  to  the  boiling  point  for  a few 
hours  and  observing  the  character  and  color  of  the  fracture 
after  sufficient  immersion,  information  as  to  the  character  of 
the  material,  whether  hydraulic,  a Portland  or  Puzzolan, 
whether  too  fresh  or  possibly  “ blowy,”  may  be  speedily  and 
quite  well  ascertained  without  measuring  instruments. 

Many  engineers  and  users  of  cements  regard  such  simple 
tests,  taken  in  connection  with  the  weight  and  fineness  of  the 
cement  and  the  apparent  texture  and  hardness  of  the  mortars 
and  concretes  in  the  work,  sufficient  field  tests  of  a material 
of  known  repute.  The  more  elaborate  tests,  described  above, 
should  be  made  in  well-equipped  laboratories  by  skilled  cement 
testers. 


TESTING  HYDRAULIC  CEMENTS. 


2a 


CLASSIFICATION  OF  TESTS. 

The  tests  to  be  made  are  two  classes. 

(1)  Purchase  tests  on  samples  furnished  by  bidders  to  as- 
certain whether  the  bidder  may  be  held  on  the  sample  to  the 
delivery  of  suitable  material,  should  his  offer  be  accepted. 

(2)  Acceptance  tests  on  samples  taken  at  random  from 
deliveries,  to  ascertain  whether  the  material  supplied  accords 
with  the  purchase  sample,  or  is  suitable  for  the  purpose  of 
the  work,  as  stated  in  the  specifications  for  cement  supplies. 

(1)  Purchase  tests. — Under  these  specifications  bids  for  Port- 
land cements  will  be  restricted  to  brands  that  have  been  ap- 
proved af tey  at  least  three  years’  exposure  in  successful  use 
under  similar  conditions  to  those  of  the  proposed  work.  This 
specification  limits  proposals  to  manufacturers  of  cements  of 
established  repute,  and  in  so  far  lessens  the  dependence  to  be 
placed  upon  tests  of  single  samples  of  cement  in  determining 
the  probable  quality  of  the  cements  offered,  that  sample  pack- 
ages may  not  be  required  with  the  proposals  when  the  brand 
is  known  to  the  purchaser.  When  the  cement  is  not  known 
to  the  purchasing  officer  by  previous  use,  a barrel  of  it  should 
be  required  as  representing  the  quality  of  cement  to  be  sup- 
plied. A full  set  of  tests  should  be  made  from  this  sample, 
and  subsequent  deliveries  be  required  to  show  quality  at  least 
equal  to  the  sample. 

In  this  connection  it  is  advisable  in  districts  where  well- 
equipped  laboratories  have  been  established,  that  sample 
packages  of  the  cements  in  use  in  that  territory,  as  sold  in 
the  open  market,  be  obtained  and  tested  as  occasion  offers  to 
ascertain  the  characteristic  qualities  of  the  brands  as  commer- 
cial articles,  the  information  to  be  used  in  subsequent  pur- 
chases of  cements. 

When  purchase  samples  are  waived,  acceptance  tests  should 
be  based  upon  the  known  qualities  of  the  brand,  as  shown  by 
previous  tests. 

The  sample  barrel  should  not  be  broken  further  than  to 
take  therefrom  the  necessary  samples  for  testing.  After- 
wards it  should  be  put  away  in  a dry  place  and  kept  for  fur- 
ther testing,  should  the  results  obtained  be  disputed. 

(2)  Acceptance  tests.— The  tests  to  be  made  on  cements 
delivered  under  contract  depend  not  only  on  the  extent, 


24 


TESTING  HYDRAULIC  CEMENTS, 


character,  and  importance  of  the  work  itself,  but  also  on  the 
time  available  between  the  delivery  and  the  actual  use  of  the 
material. 

(a)  On  very  important  and  extensive  works,  equipped  with 
a testing  laboratory  and  adequate  storehouses,  where  cement 
ma}^  be  kept  at  least  thirty  days  before  being  required  for  use, 
full  and  elaborate  tests  should  be  made,  keeping  in  view  the 
fact  that  careful  tests  of  few  samples  are  more  valuable  than 
hurried  tests  of  many  samples. 

(b)  On  active  works  of  ordinary  character,  when  time  will 
not  permit  full  tests,  and  on  small  works  where  the  expenses 
of  a laboratoiy  are  not  justified,  the  tests  must  necessarity  be 
limited  to  such  reasonable  precautions  against  the  acceptance 
and  use  of  unfit  material  as  may  be  taken  in  the  usualty  short 
interval  between  the  receipt  and  use  of  the  material. 

Such  conditions  were  in  view  in  formulating  the  specifica- 
tion that  proposals  will  be  received  from  manufacturers  of 
such  cements  only  as  have  been  proved  by  at  least  three  }^ears’ 
use  under  similar  conditions  of  exposure.  Of  the  tests  named 
in  the  specifications  those  for  fineness,  activity  or  hydraulicity, 
specific  gravity,  weight  of  packages,  and  accelerated  tests  for 
indications  as  to  soundness,  may  be  made  within  two  da}Ts 
after  the  receipt  of  the  material  and  with  a very  small 
outlay  for  instruments. 

Cement  of  established  repute,  shown  b}T  specific  gravity 
and  fineness  to  be  property  burnt  and  ground,  or  normal  for 
the  brand,  that  will  set  hard  in  reasonable  time,  the  cakes 
snapping  with  a clean  fracture  when  broken  between  the 
fingers,  and  standing  the  tests  above  named,  may  be  accepted 
and  used  with  reasonable  certainty  of  success.  Nevertheless, 
packages  taken  at  random  from  the  deliveries  should  occasion- 
ally be  set  aside  and  samples  taken  therefrom  sent  to  a testing 
laboratoiy  for  the  more  elaborate  tests  for  tensile  strength 
(and  for  soundness  should  the  boiling  tests  not  be  conclusive). 
The  final  acceptance  and  payment  for  such  cement  as  ma}T  not 
have  been  actually  placed  in  the  work  should,  by  agreement, 
be  made  to  depend  upon  such  tests. 

In  all  cases  where  cement  has  been  long  stored  it  should  be 
carefully  tested  before  use  to  ascertain  whether  it  has  deterio- 
rated in  strength. 


TESTING  HYDRAULIC  CEMENTS. 


25 


Should  the  simple  tests  give  unsatisfactory  or  suspicious 
results,  then  a full  series  of  tests  should  be  carefulty  made. 

When  Portland  cement  is  in  question  the  specific  gravity 
and  fineness  tests  should  be  made  to  guard  against  adultera- 
tion, and  in  all  cases  test  weighings  should  be  made  to  guard 
against  short  weights. 

In  cases  where  the  amount  of  cement  or  the  importance  of 
the  work  will  not  justify  the  purchase  of  the  simple  apparatus 
required  for  the  specific  gravity,  fineness,  and  boiling  tests, 
the  cement  can  be  accepted  on  the  informal  tests  mentioned 
herein,  which  require  no  apparatus  whatever,  but  in  such 
cases  cements  well  known  to  the  purchaser  by  previous  use 
should  be  selected,  and  purchased  directly  from  the  manu- 
facturer or  his  selling  agent  in  order  that  responsibility  for 
the  cement  may  be  fixed. 

Certified  tests  by  professional  inspectors  made  as  prescribed 
herein  on  samples  taken  from  the  cement  to  be  shipped  to 
the  work,  in  a manner  analogous  to  that  customary  among 
engineers  in  the  purchase  of  structural  steel  and  iron,  may 
be  required  in  such  cases. 

SAMPLING. 

The  entire  package  from  parts  of  which  tests  are  to  be  made 
is  to  be  regarded  as  the  sample  tested.  It  should  be  marked 
with  a distinctive  mark  that  must  also  be  applied  to  any"  part 
tested.  The  package  should  be  set  aside  and  protected  against 
deterioration  until  all  results  from  tests  made  from  it  are 
reached  and  accepted  by  both  parties  to  the  contract  for 
supplies. 

Cement  drawn  from  several  sample  packages  should  not  be 
mixed  or  mingled,  but  the  individuality  of  each  sample  pack- 
age should  be  preserved. 

In  testing  it  should  be  borne  in  mind  that  a few  tests  from 
any  sample,  carefully  made,  are  more  valuable  than  many 
made  with  less  care. 

The  amount  of  material  to  be  taken  for  formal  tests  is 
indicated  herein  where  weights  of  the  constituents  of  four 
briquettes  are  given,  to  which  should  be  added  the  amount 
necessary  for  the  tests  for  specific  gravity,  activity,  and 
soundness. 


26 


TESTING  HYDRAULIC  CEMENTS. 


In  extended  tests  the  material  should  be  taken  from  the 
sample  package  from  the  heads  and  center  of  barrel,  and 
from  the  ends  and  center  of  bag,  by  such  an  instrument  as 
is  used  by  inspectors  of  flour.  All  material  taken  from  the 
same  sample  package  may  be  thoroughly  mixed  or  mingled 
and  the  tests  be  made  therefrom  as  showing  the  true  charac- 
ter of  the  contents  of  the  sample  package. 

In  making  formal  tests  at  the  work  for  acceptance  of  cement 
sample  packages  should  be  taken  at  random  from  among  sound 
packages.  The  number  taken  must  depend  upon  the  impor- 
tance and  character  of  the  work,  the  available  time,  and  the 
capacity  of  the  permanent  laboratory  force.  For  tensile 
strength  the  tests  with  sand  are  considered  the  more  impor- 
tant and  should  alwa}^s  be  made.  Tests  neat  should  be  made 
if  time  permits. 

It  is  not  necessary  in  any  case  on  a large  work  to  test  more 
than  10  per  cent  of  the  deliveries,  even  of  doubtful  cement, 
and  a much  less  number  of  samples  may  be  taken  should  no 
cause  for  distrust  be  revealed  by  the  tests  made.  In  very 
important  work  of  small  extent  each  package  may  be  tested. 
A cement  should  be  rejected  if  the  samples  show  dangerous 
variation  in  quality  or  lack  of  care  in  manufacture  and  result- 
ing lack  of  uniformity  in  the  product  without  regard  to  the 
proportion  of  failures  among  samples  tested. 

In  all  cases  in  the  use  of  cements  the  informal  or  simple 
tests  of  the  character  named  herein  should  be  constantly  car- 
ried on.  These  constitute  most  valuable  tests.  Whenever 
any  faulty  material  is  indicated  by  such  tests,  elaborate  tests 
should  be  at  once  instituted  and  should  the  fault  be  confirmed, 
the  cement  delivered  and  not  used  should  be  rejected  and  the 
use  of  the  brand  be  discontinued. 

TESTS  FOR  WEIGHT. 

From  time  to  time  packages  should  be  weighed  in  gross  and 
afterwards  the  weight  of  neat  cement  and  tare  of  the  packages 
determined.  If  short  weight  of  neat  cement  is  indicated,  a 
sufficient  number  of  packages  should  be  weighed  and  the  aver- 
age net  weight  per  package  ascertained  with  sufficient  cer- 
tainty to  afford  a satisfactory  basis  of  settlement. 


TESTING  HYDRAULIC  CEMENTS. 


27 


RECORDS. 

For  tests  at  professional  laboratories  no  general  require- 
ments as  to  records  seem  to  be  necessary.  Each  laboratory 
has  its  own  blanks  with  certificate,  and  if  a copy  of  the  speci- 
fications be  sent  with  the  samples,  the  record  returned  should 
be  sufficient.  For  records  of  formal  tests  on  the  work,  or  in 
a district  laboratory,  blank  forms  should  be  used.  It  is  desir- 
able to  have  the  specification  requirements  stated  on  the  form. 
Notations  should  be  adopted  to  show  for  each  test  that  the 
cement  passed  or  failed  or  that  the  test  was  not  made.  No 
inference  should  be  drawn  from  the  lack  of  any  entry  other 
than  that  the  recorder  has  neglected  his  duty. 

SILICA  CEMENT  OR  SAND  CEMENT. 

This  is  a patented  article  manufactured  by  grinding  together 
silica  or  clean  sand  with  Portland  cement,  by  which  process 
the  original  cementing  material  is  made  extremely  fine  and  its 
capacity  to  cover  surfaces  of  concrete  aggregates  is  much  in- 
creased. The  sand  is  an  adulteration,  but  on  account  of  the 
extreme  fineness  of  the  product  it  serves  to  make  mortar  or 
concrete  containing  a given  proportion  of  pure  cement  much 
more  dense,  the  fine  material  being  increased  in  volume. 

The  increase  in  cementing  capacity  due  to  the  fine  grinding 
of  the  cement  constituent  offsets,  in  great  degree,  the  effects 
of  the  sand  adulteration,  so  that  sand  cement  made  from  equal 
weights  of  cement  and  sand  approximates  in  tensile  strength 
to  the  neat  cement  and  the  material  is  sold  as  cement. 

The  extreme  fine  grinding  also  improves  cement  that  con- 
tains expansives,  but  nevertheless  sand  cement  should  not  be 
purchased  in  the  market,  but  should  be  made  on  the  work  from 
approved  materials,  if  used  for  other  purposes  than  for  grout- 
ing, for  which  it  is  peculiarly  adapted. 

Whether  this  material  should  be  used  in  important  works 
for  mortar  and  concrete,  the  Board  considers  a question  of 
cost  and  expediency. 

Over  against  the  saving  in  cement  may  be  placed  the 
royalty  on  a patented  article,  the  cost  of  the  plant  and  of 
manufacture,  the  inconvenience  of  attaching  a manufacturing 
establishment  to  a work  under  construction,  and  other  ele- 


28 


TESTING  HYDRAULIC  CEMENTS. 


merits  bearing  not  only  on  first  cost  of  cementing  material 
but  also  involving  the  element  of  time.  When  cement  is 
high  priced,  means  of  transportation  limited,  labor,  sand, 
and  concrete  materials  cheap  and  abundant,  the  conditions 
may  justify  the  use  of  sand  cement  on  economic  grounds.  In 
any  case,  the  cement  from  which  the  product  is  made  should 
be  tested  precisely  as  other  cements. 

SLAG  CEMENT. 

This  term  is  applied  to  cement  made  by  intimately  mixing 
by  grinding  together  granulated  blast-furnace  slag  of  a cer- 
tain quality  and  slaked  lime,  without  calcination  subsequent 
to  the  mixing.  This  is  the  only  cement  of  the  Puzzolan  class 
to  be  found  in  our  markets  (often  branded  as  Portland),  and 
as  true  Portland  cement  is  now  made  having  slag  for  its 
hydraulic  base,  the  term  “slag  cement”  should  be  dropped 
and  the  generic  term  Puzzolan  be  used  in  advertisements  and 
specifications  for  such  cements. 

Puzzolan  cement  made  from  slag  is  characterized  physically 
by  its  light  lilac  color;  the  absence  of  grit  attending  fine  grind- 
ing and  the  extreme  subdivision  of  its  slaked  lime  element; 
its  low  specific  gravity  (2.6  to  2.8)  compared  with  Portland 
(3  to  3.5);  and  by  the  intense  bluish  green  color  in  the  fresh 
fracture  after  long  submersion  in  water,  due  to  the  presence 
of  sulphides,  which  color  fades  after  exposure  to  dry  air. 

The  oxidation  of  sulphides  in  dry  air  is  destructive  of  Puz- 
zolan cement  mortars  and  concretes  so  exposed.  Puzzolan  is 
usually  very  finely  ground,  and  when  not  treated  with  soda 
sets  more  slowly  than  Portland.  It  stands  storage  well,  but 
cements  treated  with  soda  to  quicken  setting  become  again 
very  slow  setting  from  the  carbonization  of  the  soda  (as  well 
as  the  lime)  element  after  long  storage. 

Puzzolan  cement  properl}"  made  contains  no  free  or  anhy- 
drous lime,  does  not  warp  or  swell,  but  is  liable  to  fail  from 
cracking  and  shrinking  (at  the  surface  only)  in  dry  air. 

Mortars  and  concretes  made  from  Puzzolan  approximate  in 
tensile  strength  similar  mixtures  of  Portland  cement,  but 
their  resistance  to  crushing  is  less,  the  ratio  of  crushing  to 
tensile  strength  being’  about  6 or  T to  1 for  Puzzolan  and  9 to 
11  to  1 for  Portland.  On  account  of  its  extreme  fine  grind- 


TESTING  HYDRAULIC  CEMENTS. 


29 


ing  Puzzolan  often  gives  nearly  as  great  tensile  strength  in  3 
to  1 mixtures  as  neat. 

Puzzolan  permanently  assimilates  but  little  water  compared 
with  Portland,  its  lime  being  already  hydrated,  It  should  be 
used  in  comparatively  dry  mixtures  well  rammed,  but  while 
requiring  little  water  for  chemical  reactions,  it  requires  for 
permanency  in  the  air  constant  or  continuous  moisture. 

PROPER  USES  OF  PUZZOLAN  CEMENT. 

Puzzolan  cement  never  becomes  extremely  hard  like  Port- 
land, but  Puzzolan  mortars  and  concretes  are  tougher  or  less 
brittle  than  Portland. 

The  cement  is  well  adapted  for  use  in  sea  water,  and  gen- 
erally in  all  positions  where  constantly  exposed  to  moisture, 
such  as  in  foundations  of  buildings,  sewers  and  drains,  and 
underground  works  generally,  and  in  the  interior  of  heavy 
masses  of  masonry  or  concrete. 

It  is  unfit  for  use  when  subjected  to  mechanical  wear,  attri- 
tion, or  blows.  It  should  never  be  used  where  it  may  be  ex- 
posed for  long  periods  to  dry  air,  even  after  it  has  well  set.  It 
will  turn  white  and  disintegrate,  due  to  the  oxidation  of  its 
sulphides  at  the  surface  under  such  exposure. 

Specifications  for  Portland,  Natural,  and  Puzzolan  cement 
are  appended  hereto. 

Kespectfully  submitted. 

W.  L.  Marshall, 

Major , Corps  of  Engineers. 

Smith  S.  Leach, 

Major , Corps  of  Engineers. 

Spencer  Cosby, 

Captain , Corps  of  Engineers. 

Brig.  Gen.  G.  L.  Gillespie, 

Corps  of  Engineers,  JJ.  S.  Army , 

Washington , D.  C. 


30 


TESTING  HYDRAULIC  CEMENTS. 


SPECIFICATIONS  FOR  AMERICAN  PORTLAND 
CEMENT. 

(1)  The  cement  shall  be  an  American  Portland,  dry  and  free 
from  lumps.  By  a Portland  cement  is  meant  the  product 
obtained  from  the  heating  or  calcining  up  to  incipient  fusion 
of  intimate  mixtures,  either  natural  or  artifical,  of  argillaceous 
with  calcareous  substances,  the  calcined  product  to  contain  at 
least  1.7  times  as  much  of  lime,  by  weight,  as  of  the  materials 
which  give  the  lime  its  hydraulic  properties,  and  to  be  finely 
pulverized  after  said  calcination,  and  thereafter  additions  or 
substitutions  for  the  purpose  only  of  regulating  certain  prop- 
erties of  technical  importance  to  be  allowable  to  not  exceed- 
ing 2 per  cent  of  the  calcined  product. 

(2)  The  cement  shall  be  put  up  in  strong,  sound  barrels  well 
lined  with  paper,  so  as  to  be  reasonably  protected  against 
moisture,  or  in  stout  cloth  or  canvas  sacks.  Each  package 
shall  be  plainly  labeled  with  the  name  of  the  brand  and  of  the 
manufacturer.  Any  package  broken  or  containing  damaged 
cement  may  be  rejected  or  accepted  as  a fractional  package,  at 
the  option  of  the  United  States  agent  in  local  charge. 

(3)  Bidders  will  state  the  brand  of  cement  which  they  pro- 
pose to  furnish.  The  right  is  reserved  to  reject  a tender  for 
any  brand  which  has  not  established  itself  as  a high-grade 
Portland  cement  and  has  not  for  three  years  or  more  given 
satisfaction  in  use  under  climatic  or  other  conditions  of  ex- 
posure of  at  least  equal  severity  to  those  of  the  work  proposed. 

(4)  Tenders  will  be  received  only  from  manufacturers  or 
their  authorized  agents. 

(The  following  paragraph  will  be  substituted  for  paragraphs 
3 and  4 above  when  cement  is  to  be  furnished  and  placed  by 
the  contractor: 

No  cement  will  be  allowed  to  be  used  except  established 
brands  of  high-grade  Portland  cement  which  have  been  made 
by  the  same  mill  and  in  successful  use  under  similar  climatic 
conditions  to  those  of  the  proposed  work  for  at  least  three 
years. ) 

(5)  The  average  weight  per  barrel  shall  not  be  less  than  375 
pounds  net.  Pour  sacks  shall  contain  one  barrel  of  cement. 
If  the  weight,  as  determined  b}r  test  weighings,  is  found  to 
be  below  375  pounds  per  barrel,  the  cement  may  be  rejected, 


TESTING  HYDRAULIC  CEMENTS. 


31 


or,  at  the  option  of  the  engineer  officer  in  charge,  the  con- 
tractor may  be  required  to  suppl}r,  free  of  cost  to  the  United 
States,  an  additional  amount  of  cement  equal  to  the  shortage. 

(6)  Tests  may  be  made  of  the  fineness,  specific  gravity, 
soundness,  time  of  setting,  and  tensile  strength  of  the  cement. 

(7)  Fineness. — Ninety-two  per  cent  of  the  cement  must  pass 
through  a sieve  made  of  No.  10  wire,  Stubb’s  gauge,  having 
10,000  openings  per  square  inch. 

(8)  Specific  gravity . — The  specific  gravity  of  the  cement,  as 
determined  from  a sample  which  has  been  carefully  dried, 
shall  be  between  3.10  and  3.25. 

(9)  Soundness. — To  test  the  soundness  of  the  cement,  at  least 
two  pats  of  neat  cement  mixed  for  five  minutes  with  20  per 
cent  of  water  by  weight  shall  be  made  on  glass,  each  pat  about 
3 inches  in  diameter  and  one-half  inch  thick  at  the  center, 
tapering  thence  to  a thin  edge.  The  pats  are  to  be  kept 
under  a wet  cloth  until  finall}7  set,  when  one  is  to  be  placed  in 
fresh  water  for  twenty-eight  days.  The  second  pat  will  be 
placed  in  water  which  will  be  raised  to  the  boiling  point  for  six 
hours,  then  allowed  to  cool.  Neither  should  show  distortion 
or  cracks.  The  boiling  test  may  or  may  not  reject  at  the  op- 
tion of  the  engineer  officer  in  charge. 

(10)  Time  of  setting. — The  cement  shall  not  acquire  its 
initial  set  in  less  than  forty-five  minutes  and  must  have 
acquired  its  final  set  in  ten  hours. 

(The  following  paragraph  will  be  substituted  for  the  above 
in  case  a quick-setting  cement  is  desired: 

The  cement  shall  not  acquire  its  initial  set  in  less  than  twenty 
nor  more  than  thirty  minutes,  and  must  have  acquired  its  final 
set  in  not  less  than  forty-five  minutes  nor  in  more  than  two 
and  one-half  hours.) 

The  pats  made  to  test  the  soundness  may  be  used  in  deter- 
mining the  time  of  setting.  The  cement  is  considered  to  have 
acquired  its  initial  set  when  the  pat  will  bear,  without  being 
appreciably  indented,  a wire  one-twelfth  inch  in  diameter 
loaded  to  weigh  one-fourth  pound.  The  final  set  has  been 
acquired  when  the  pat  will  bear,  without  being  appreciably 
indented,  a wire  one  twenty-fourth  inch  in  diameter  loaded 
to  weigh  1 pound. 

(11)  Tensile  strength. — Briquettes  made  of  neat  cement, 
after  being  kept  in  air  for  twenty-four  hours  under  a wet 


82 


TESTING  HYDKAULIC  CEMENTS. 


cloth  and  the  balance  of  the  time  in  water,  shall  develop  ten- 
sile strength  per  square  inch  as  follows: 

After  seven  days,  450  pounds;  after  twenty-eight  days,  540 
pounds. 

Briquettes  made  of  1 part  cement  and  3 parts  standard  sand, 
by  weight,  shall  develop  tensile  strength  per  square  inch  as 
follows : 

After  seven  days,  140  pounds;  after  twenty-eight  days,  220 
pounds. 

(In  case  quick-setting  cement  is  desired,  the  following  ten- 
sile strengths  shall  be  substituted  for  the  above: 

Neat  briquettes:  After  seven  days,  400  pounds;  after  twenty- 
eight  da}rs,  480  pounds. 

Briquettes  of  1 part  cement  to  3 parts  standard  sand:  After 
seven  days,  120  pounds;  after  twenty-eight  days,  180  pounds.) 

(12)  The  highest  result  from  each  set  of  briquettes  made  at 
any  one  time  is  to  be  considered  the  governing  test.  Any 
cement  not  showing  an  increase  of  strength  in  the  twenty- 
eight-day  tests  over  the  seven-day  tests  will  be  rejected. 

(13)  When  making  briquettes  neat  cement  will  be  mixed 
with  20  per  cent  of  water  by  weight,  and  sand  and  cement 
with  12i  per  cent  of  water  by  weight.  After  being  thor- 
ough^ mixed  and  worked  for  live  minutes,  the  cement  or  mor- 
tar will  be  placed  in  the  briquette  mold  in  four  equal  layers, 
and  each  layer  rammed  and  compressed  by  thirty  blows  of  a 
soft  brass  or  copper  rammer  three-quarters  of  an  inch  in 
diameter  (or  seven-tenths  of  an  inch  square,  with  rounded  cor- 
ners), weighing  1 pound.  It  is  to  be  allowed  to  drop  on  the 
mixture  from  a height  of  about  half  an  inch.  When  the  ram- 
ming has  been  completed,  the  surplus  cement  shall  be  struck 
off  and  the  final  layer  smoothed  with  a trowel  held  almost  hori- 
zontal and  drawn  back  with  sufficient  pressure  to  make  its  edge 
follow  the  surface  of  the  mold. 

(14)  The  above  are  to  be  considered  the  minimum  require- 
ments. Unless  a cement  has  been  recently  used  on  work 
under  this  office,  bidders  will  deliver  a sample  barrel  for  test 
before  the  opening  of  bids.  If  this  sample  shows  higher  tests 
than  those  given  above,  the  average  of  tests  made  on  subse- 
quent shipments  must  come  up  to  those  found  with  the  sample. 

(15)  A cement  may  be  rejected  in  case  it  fails  to  meet  any 
of  the  above  requirements.  An  agent  of  the  contractor  may 


TESTING  HYDKAULIC  CEMENTS. 


33 


be  present  at  the  making  of  the  tests,  or,  in  case  of  the  fail- 
ure of  any  of  them,  they  may  be  repeated  in  his  presence. 
If  the  contractor  so  desires,  the  engineer  officer  in  charge 
may,  if  he  deem  it  to  the  interest  of  the  United  States,  have 
any  or  all  of  the  tests  made  or  repeated  at  some  recognized 
standard  testing  laboratory  in  the  manner  herein  specified. 
All  expenses  of  such  tests  to  be  paid  by  the  contractor.  All 
such  tests  shall  be  made  on  samples  furnished  by  the  engineer 
officer  from  cement  actually  delivered  to  him. 


SPECIFICATIONS  FOR  NATURAE  CEMENT. 

(1)  The  cement  shall  be  a freshly  packed  natural  or  Rosen- 
dale,  dry,  and  free  from  lumps.  By  Natural  cement  is  meant 
one  made  by  calcining  natural  rock  at  a heat  below  incipient 
fusion,  and  grinding  the  product  to  powder. 

(2)  The  cement  shall  be  put  up  in  strong,  sound  barrels,  well 
lined  with  paper  so  as  to  be  reasonably  protected  against  mois- 
ture, or  in  stout  doth  or  canvas  sacks.  Each  package  shall  be 
plainly  labeled  with  the  name  of  the  brand  and  of  the  manu- 
facturer. Any  package  broken  or  containing  damaged  cement 
may  be  rejected,  or  accepted  as  a fractional  package,  at  the 
option  of  the  United  States  agent  in  local  charge. 

(3)  Bidders  will  state  the  brand  of  cement  which  they  pro- 
pose to  furnish.  The  right  is  reserved  to  reject  a tender  for 
any  brand  which  has  not  given  satisfaction  in  use  under  cli- 
matic or  other  conditions  of  exposure  of  at  least  equal  severity 
to  those  of  the  work  proposed. 

(4)  Tenders  will  be  received  only  from  manufacturers  or 
their  authorized  agents. 

(The  following  paragraph  will  be  substituted  for  paragraphs 
3 and  4 above  when  cement  is  to  be  furnished  and  placed  by 
the  contractor: 

No  cement  will  be  allowed  to  be  used  except  established 
brands  of  high-grade  natural  cement  which  have  been  in  suc- 
cessful use  under  similar  climatic  conditions  to  those  of  the 
proposed  work.) 

(5)  The  average  net  weight  per  barrel  shall  not  be  less  than 

300  pounds.  (West  of  the  Allegheny  Mountains  this  may  be 
265  pounds.)  . . . sacks  of  cement  shall  have  the  same 

1593—01 3 


34 


TESTING  HYDRAULIC  CEMENTS. 


weight  as  1 barrel.  If  the  average  net  weight,  as  determined 
by  test  weighings,  is  found  to  be  below  300  pounds  (265 
pounds)  per  barrel,  the  cement  may  be  rejected,  or,  at  the 
option  of  the  engineer  officer  in  charge,  the  contractor  may 
be  required  to  supply  free  of  cost  to  the  United  States  an 
additional  amount  of  cement  equal  to  the  shortage. 

(6)  Tests  may  be  made  of  the  fineness,  time  of  setting,  and 
tensile  strength  of  the  cement. 

(7)  Fineness. — At  least  80  per  cent  of  the  cement  must  pass 
through  a sieve  made  of  No.  40  wire,  Stubb’s  gauge,  having 
10,000  openings  per  square  inch. 

(8)  Time  of  setting. — The  cement  shall  not  acquire  its  initial 
set  in  less  than  twenty  minutes  and  must  have  acquired  its 
final  set  in  four  hours. 

(9)  The  time  of  setting  is  to  be  determined  from  a pat  of 
neat  cement  mixed  for  five  minutes  with  30  per  cent  of  water 
by  weight  and  kept  under  a wet  cloth  until  finally  set.  The 
cement  is  considered  to  have  acquired  its  initial  set  when  the 
pat  will  bear,  without  being  appreciabty  indented,  a wire  one- 
twelfth  inch  in  diameter  loaded  to  weigh  one-fourth  pound. 
The  final  set  has  been  acquired  when  the  pat  will  bear,  with- 
out being  appreciably  indented,  a wire  one  twenty-fourth  inch 
in  diameter  loaded  to  weigh  1 pound. 

(10)  Tensile  strength. — Briquettes  made  of  neat  cement 
shall  develop  the  following  tensile  strengths  per  square  inch, 
after  having  been  kept  in  air  for  twenty-four  hours  under  a 
wet  cloth  and  the  balance  of  the  time  in  water: 

At  the  end  of  seven  days,  90  pounds;  at  the  end  of  twenty- 
eight  days,  200  pounds. 

Briquettes  made  of  one  part  cement  and  one  part  standard 
sand  by  weight  shall  develop  the  following  tensile  strengths 
per  square  inch: 

After  seven  days,  60  pounds;  after  twenty-eight  days,  150 
pounds. 

(11)  The  highest  result  from  each  set  of  briquettes  made  at 
any  one  time  is  to  be  considered  the  governing  test.  Any 
cement  not  showing  an  increase  of  strength  in  the  twenty-eight 
day  tests  over  the  seven-day'  tests  will  be  rejected. 

(12)  The  neat  cement  for  briquettes  shall  be  mixed  with  30 
per  cent  of  water  by  weight,  and  the  sand  and  cement  with  17 
per  cent  of  water  by  weight.  After  being  thoroughly  mixed 


TESTING  HYDRAULIC  CEMENTS. 


35 


and  worked  for  five  minutes  the  cement  or  mortar  is  to  be 
placed  in  the  briquette  mold  in  four  equal  layers,  each  of 
which  is  to  be  rammed  and  compressed  by  thirty  blows  of 
a soft  brass  or  copper  rammer  three-fourths  of  an  inch  in 
diameter  (or  seven-tenths  of  an  inch  square  with  rounded  cor- 
ners), weighing  1 pound.  It  is  to  be  allowed  to  drop  on  the 
mixture  from  a height  of  about  half  an  inch.  Upon  the  com- 
pletion of  the  ramming  the  surplus  cement  shall  be  struck  off 
and  the  last  layer  smoothed  with  a trowel  held  nearly  horizon- 
tal and  drawn  back  with  sufficient  pressure  to  make  its  edge 
follow  the  surface  of  the  mold. 

(13)  The  above  are  to  be  considered  the  minimum  require- 
ments. Unless  a cement  has  been  recently  used  on  work 
under  this  office,  bidders  will  deliver  a sample  barrel  for  test 
before  the  opening  of  the  bids.  Any  cement  showing  by 
sample,  higher  tests  than  those  given  must  maintain  the 
average  so  shown  in  subsequent  deliveries. 

(14)  A cement  may  be  rejected  which  fails  to  meet  any  of 
the  above  requirements.  An  agent  of  the  contractor  may  be 
present  at  the  making  of  the  tests,  or,  in  case  of  the  failure 
of  any  of  them,  they  may  be  repeated  in  his  presence.  If 
the  contractor  so  desires,  the  engineer  officer  may,  if  he 
deems  it  to  the  interest  of  the  United  States,  have  any  or  all 
of  the  tests  made  or  repeated  at  some  recognized  standard 
testing  laboratory  in  the  manner  above  specified.  All  ex- 
penses of  such  tests  shall  be  paid  by  the  contractor,  and  all 
such  tests  shall  be  made  on  samples  furnished  by  the  engineer 
officer  from  cement  actually  delivered  to  him. 


SPECIFICATIONS  FOR  PIJZZOEAN  CEMENT. 

(1)  The  cement  shall  be  a Puzzolan  of  uniform  quality, 
finely  and  freshly  ground,  dry,  and  free  from  lumps,  made  by 
grinding  together  without  subsequent  calcination  granulated 
blast-furnace  slag  with  slaked  lime. 

(2)  The  cement  shall  be  put  up  in  strong  sound  barrels  well 
lined  with  paper,  so  as  to  be  reasonably  protected  against 
moisture,  or  in  stout  cloth  or  canvas  sacks.  Each  package 
shall  be  plainty  labeled  with  the  name  of  the  brand  and  of  the 


36 


TESTING  HYDRAULIC  CEMENTS. 


manufacturer.  An}^  package  broken  or  containing  damaged 
cement  may  be  rejected,  or  accepted  as  a fractional  package, 
at  the  option  of  the  United  States  agent  in  local  charge. 

(3)  Bidders  will  state  the  brand  of  cement  which  they  pro- 
pose to  furnish.  The  right  is  reserved  to  reject  a tender  for 
any  brand  which  has  not  given  satisfaction  in  use  under  cli- 
matic or  other  conditions  of  exposure  of  at  least  equal  severity 
to  those  of  the  work  proposed,  and  for  any  brand  from  cement 
works  that  do  not  make  and  test  the  slag  used  in  the  cement. 

(4)  Tenders  will  be  received  only  from  manufacturers  or 
their  authorized  agents. 

(The  following  paragraph  will  be  substituted  for  paragraphs 
3 and  4 above  when  cement  is  to  be  furnished  and  placed  by 
the  contractor: 

No  cement  will  be  allowed  to  be  used  except  established 
brands  of  high-grade  Puzzolan  cement  which  have  been  in 
successful  use  under  similar  climatic  conditions  to  those  of 
the  proposed  work  and  which  come  from  cement  works  that 
make  the  slag  used  in  the  cement.) 

(5)  The  average  weight  per  barrel  shall  not  be  less  than  330 
pounds  net.  Four  sacks  shall  contain  1 barrel  of  cement. 
If  the  weight  as  determined  by  test  weighings  is  found  to  be 
below  330  pounds  per  barrel,  the  cement  may  be  rejected  or, 
at  the  option  of  the  engineer  officer  in  charge,  the  contractor 
may  be  required  to  supply,  free  of  cost  to  the  United  States, 
an  additional  amount  of  cement  equal  to  the  shortage. 

(6)  Tests  may  be  made  of  the  lineness,  specific  gravity, 
soundness,  time  of  setting,  and  tensile  strength  of  the  cement. 

(7)  Fineness.—  Ninety-seven  per  cent  of  the  cement  must 
pass  through  a sieve  made  of  No.  40  wire,  Stubb’s  gauge, 
having  10,000  openings  per  square  inch. 

(8)  Specific  gravity. — The  specific  gravity  of  the  cement,  as 
determined  from  a sample  which  has  been  carefully  dried, 
shall  be  between  2.7  and  2.8. 

(9)  Soundness. — To  test  the  soundness  of  cement,  pats  of 
neat  cement  mixed  for  five  minutes  with  18  per  cent  of  water 
by  weight  shall  be  made  on  glass,  each  pat  about  3 inches  in 
diameter  and  one-half  inch  thick  at  the  center,  tapering  thence 
to  a thin  edge.  The  pats  are  to  be  kept  under  wet  cloths  until 
finally  set,  when  they  are  to  be  placed  in  fresh  water.  They 
should  not  show  distortion  or  cracks  at  the  end  of  twenty-eight 
days. 


TESTING  HYDRAULIC  CEMENTS. 


37 


(10)  Time  of  setting. — The  cement  shall  not  acquire  its  ini- 
tial set  in  less  than  forty-five  minutes  and  shall  acquire  its 
final  set  in  ten  hours.  The  pats  made  to  test  the  soundness 
ma}r  be  used  in  determining  the  time  of  setting.  The  cement 
is  considered  to  have  acquired  its  initial  set  when  the  pat  will 
bear,  without  being  appreciably  indented,  a wire  one-twelfth 
inch  in  diameter  loaded  to  one-fourth  pound  weight.  The 
final  set  has  been  acquired  when  the  pat  will  bear,  without 
being  appreciably  indented,  a wire  one  twenty-fourth  inch  in 
diameter  .loaded  to  1 pound  weight. 

(11)  Tensile  strength. — Briquettes  made  of  neat  cement, 
after  being  kept  in  air  under  a wet  cloth  for  twenty-four 
hours  and  the  balance  of  the  time  in  water,  shall  develop  ten- 
sile strengths  per  square  inch  as  follows: 

After  seven  da}^s,  350  pounds;  after  twenty-eight  days,  500 
pounds. 

Briquettes  made  of  one  part  cement  and  three  parts  stand- 
ard sand  by  weight  shall  develop  tensile  strength  per  square 
inch  as  follows: 

After  seven  da3^s,  140  pounds;  after  twenty-eight,  days,  220 
pounds. 

(12)  The  highest  result  from  each  set  of  briquettes  made  at 
any  one  time  is  to  be  considered  the  governing  test.  Any 
cement  not  showing  an  increase  of  strength  in  the  twenty- 
eight-day  tests  over  the  seven-day  tests  will  be  rejected. 

(13)  When  making  briquettes  neat  cement  will  be  mixed 
with  18  per  cent  of  water  by  weight,  and  sand  and  cement 
with  10  per  cent  of  water  by  weight.  After  being  thoroughly 
mixed  and  worked  for  five  minutes  the  cement  or  mortar 
will  be  placed  in  the  briquette  mold  in  four  equal  layers  and 
each  layer  rammed  and  compressed  by  thirty  blows  of  a soft 
brass  or  copper  rammer,  three-quarters  of  an  inch  in  diameter 
or  seven-tenths  of  an  inch  square,  with  rounded  corners, 
weighing  1 pound.  It  is  to  be  allowed  to  drop  on  the  mixture 
from  a height  of  about  half  an  inch.  When  the  ramming  has 
been  completed  the  surplus  cement  shall  be  struck  off  and  the 
final  layer  smoothed  with  a trowel  held  almost  horizontal  and 
drawn  back  with  sufficient  pressure  to  make  its  edge  follow 
the  surface  of  the  mold. 

(14)  The  above  are  to  be  considered  the  minimum  require- 
ments. Unless  a cement  has  been  recently  used  on  work 


38 


TESTING  HYDRAULIC  CEMENTS. 


under  this  office,  bidders  will  deliver  a sample  barrel  for  test 
before  the  opening  of  bids.  If  this  sample  shows  higher  tests 
than  those  given  above,  the  average  of  tests  made  on  subse- 
quent shipments  must  come  up  to  those  found  with  the  sample. 

(15)  A cement  may  be  rejected  in  case  it  fails  to  meet  any 
of  the  above  requirements.  An  agent  of  the  contractor  may 
be  present  at  the  making  of  the  tests,  or,  in  case  of  the  failure 
of  any  of  them,  they  may  be  repeated  in  his  presence.  If  the 
contractor  so  desires  the  engineer  officer  in  charge  may,  if 
he  deems  it  to  the  interest  of  the  United  States,  have  an}7  or 
all  of  the  tests  made  or  repeated  at  some  recognized  testing 
laboratory  in  the  manner  herein  specified,  all  expenses  of  such 
tests  to  be  paid  by  the  contractor.  All  such  tests  shall  be 
made  on  samples  furnished  by  the  engineer  officer  from 
cement  actually  delivered  to  him. 


O 


I 


